Vehicle stability control system

• US 20050200088A1
• Filed: 03/09/2005
• Published: 09/15/2005
• Est. Priority Date: 03/09/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sawada, Mamoru, Matsumoto, Toshiki
• Granted Patent: US 7,577,504 B2
• Time in Patent Office: Days
• US Class Current: 280/5.507
• CPC Class Codes: B60W 10/04 including control of propulsion units
• CPC Class Codes: B60W 2510/20 Steering systems
• CPC Class Codes: B60W 30/045 Improving turning performance

Abstract

A vehicle stability control system includes a basic request driving force computing unit, a front and rear wheel load computing unit, a virtual turning radius estimating unit, a target value computing unit, and a vibration damping correction controlling unit. The basic request driving force computing unit computes a physical quantity so as to generate the basic request driving force requested by a driver. The front and rear wheel load computing unit detect a load applied to the wheels. The virtual turning radius estimating unit estimates a virtual turning radius. The target value computing unit computes a target value of a stability factor. The vibration damping correction controlling unit corrects the physical quantity so as to follow the target value. The system generates the driving force for the driving wheel.

Claims

1. A vehicle stability control system comprising:

a basic request driving force computing unit for computing a physical quantity corresponding to a basic request driving force so as to generate the basic request driving force requested by a driver for a driving wheel provided for a vehicle;

a front and rear wheel load computing unit for detecting a ground load applied to each of front wheels and rear wheels in the vehicle;

a virtual turning radius estimating unit for estimating a virtual turning radius in the vehicle;

a target value computing unit for computing a target value of a stability factor based on the results of computations in the front and rear wheel load computing unit and the virtual turning radius estimating unit; and

a vibration damping correction controlling unit for correcting a physical quantity corresponding to the basic request driving force computed by the basic request driving force computing unit so as to follow the target value computed by the target value computing unit, wherein

a driving force in accordance with the corrected physical quantity corrected by the vibration damping correction controlling unit is generated for the driving wheel.

2. The vehicle stability control system according to claim 1, wherein the basic request driving force computing unit computes a basic request torque as the physical quantity corresponding to the basic request driving force.

3. The vehicle stability control system according to claim 1, wherein the front and rear wheel ground load computing unit computes front and rear wheel static ground loads respectively applied to the front wheel and the rear wheel when the vehicle is running in a steady state, as the front and rear wheel ground loads, and

the target value computing unit computes the target value of the stability factor based on the front and rear wheel static ground loads.

4. The vehicle stability control system according to claim 1, comprising an estimated road grade calculating unit for estimating a grade of the road surface on which the vehicle is running, wherein

the front and rear wheel ground load computing unit computes front and rear static ground loads respectively applied to the front wheel and the rear wheel when the vehicle is running in a steady state, as the front and rear wheel ground loads, and computes an amount of fluctuation in the front and rear wheel ground loads, in the case where the vehicle runs in the steady state on the estimated road grade based on the estimated road grade computed in the estimated road grade calculating unit, so as to obtain a value taking the amounts of fluctuation generated by the estimated road grade into account from the front and rear wheel static ground loads as front and rear wheel ground loads, and

the target value computing unit computes the target value of the stability factor based on the front and rear wheel ground loads taking the amounts of fluctuation in the front and rear wheel ground loads generated by the estimated road grade into account.

5. The vehicle stability control system according to claim 1, wherein the vibration damping correction controlling unit includes a state equation indicating a state quantity in the vehicle based on a sprung oscillation model in the vehicle and an output equation expressing the stability factor as the state quantity based on the state equation so as to correct the physical quantity corresponding to the basic request driving force based on a difference between the stability factor obtained from the output equation and the state quantity and the target value of the stability factor computed in the target value computing unit.

6. The vehicle stability control system according to claim 5, comprising a running resistance disturbance estimating unit for estimating a running resistance disturbance applied to the wheels in the vehicle, wherein

the vibration damping correction controlling unit obtains the state quantity in the state equation in view of the running resistance disturbance estimated by the running resistance disturbance estimating unit so as to obtain the stability factor based on the obtained state quantity and the output equation and to obtain a difference between the stability factor and the target value.

7. The vehicle stability control system according to claim 6, wherein the running resistance disturbance estimating unit obtains a running resistance disturbance of the front wheel as the running resistance disturbance, based on a derivative value of a wheel speed of the front wheel provided for the vehicle and the weight of the vehicle.

8. The vehicle stability control system according to claim 1, comprising image recognition means for taking an image of an external circumstance of the vehicle and for outputting image data, wherein

the virtual turning radius estimating unit estimates the virtual turning radius based on an optical flow of the image data of the vehicle-mounted camera.

9. The vehicle stability control system according to claim 8, wherein the virtual turning radius estimating unit sets the virtual turning radius so that the vehicle gives priority to a lateral translational motion rather than to a turning motion in the case where an obstacle is present in the image data in the image recognition means and the obstacle is distant from the own vehicle by a predetermined distance or more whereas the virtual turning radius estimating unit sets the virtual turning radius so that the vehicle gives priority to the turning motion rather than to the lateral translational motion in the case where the obstacle is close to the own vehicle to be within the predetermined distance.

10. The vehicle stability control system according to claim 8, comprising vehicle speed detection means for generating an output in accordance with a vehicle speed in the vehicle, wherein

the virtual turning radius estimating unit sets the virtual turning radius so that the vehicle gives priority to the lateral translational motion rather than to the turning motion when the vehicle speed detected by the vehicle speed detection means is higher than a predetermined speed and the vehicle is running at high speed, whereas the virtual turning radius estimating unit sets the virtual turning radius so that the vehicle gives priority to the turning motion rather than to the lateral translational motion when the vehicle speed detected by the vehicle speed detection means is lower than the predetermined speed and the vehicle is running at low speed.